Broadcast radio stations, such FM radio stations, may use a system known as a Radio Data System (RDS) or Radio Broadcast Data System (RBDS in US), both referred to herein as “RDS,” to transmit supplemental information corresponding to their normal radio programming, e.g., music, talk, news, etc. In particular, RDS is intended for application to FM sound broadcasts between 87.5 MHz to 108.0 MHz. For stereophonic broadcast, the RDS subcarrier is locked to third harmonic of the 19 KHz pilot tone with overall tolerance of ±6 Hz. For monophonic broadcast, the RDS subcarrier is 57 KHz±6 Hz. The data message rate is constrained to 1.1875 Kbits/sec as defined in standards for RBDS (i.e., NRSC-4-A, National Radio Systems Committee (NRSC) jointly sponsored by Consumer Electronics Association (CEA) and National Association of Broadcasters (NAB)) and for RDS (i.e., IEC/CENELEC EN:62106:2001, International Electrotechnical Commission (IEC) and European Committee for Electrotechnical Standardization (CENELEC)).
Broadcast radio stations transmit their programming and the supplemental information in the RDS format as distinct signals multiplexed onto a single carrier. Radio receivers having RDS decoders, such as those included with some wireless communications devices or those in a vehicle, permit a user to listen to the transmitted programming and view the corresponding supplemental information on a display. Specifically, generally-known RDS improves functionality for FM receivers by providing basic RDS information such as Program Identification, Program Service, and Automatic tuning as well as Open Data Application (ODA) for such services as traffic message channel, emergency warning systems, radio text, and enhanced radio paging, etc.
Attempts have been made to extend RDS beyond providing a standard protocol for several types of supplemental information transmitted by the broadcast radio stations, such as the identity of the particular radio station, the type of programming, and text information such as the name of an artist and/or song. For example, some specifications provide additional messages that can control portions of the supplemental information, such as the display of the radio text information. In another example, some services have been developed to provide content to the receiver using a data connection, where the content is synchronized with the radio programming via the data message.